312 P. E. Chase on the relations of Gravity and Magnetism. 
copper districts in the world. Silver and lead ores occur in 
abundance, but I will not undertake to describe here the various 
localities of them which we have seen, or the specimens which 
we have collected. 
am fully convinced that this portion of Mexico, when prop- 
erly opened by the application of intelligent enterprise, will prove 
one of the richest mining regions of America. 
ArT. XXXIX.--Numerical Relations of Gravity and Magnetism; 
by Puiny Earue Cuass, M.A., S.P.A.S. 
The mutual convertibility of Light, Heat, Electricity, Mag: 
netism, Chemical Affinity, and Vital Energy, ma is 
earth, provided the magnetic axis corresponded with the axis 
rotati 
* Brom the Proceedings of the American Philosophical Society, Dec. 16, 1864 
The Magellanic Gold Medal was awarded the author for this memoir. 5, 1864. 
| This t was first announced by me, at the Society’s meeting, April 15, 
See Proc. A. PS. ix, 367. 
2 
